Bismarck and Darius are probably the two I'd pick (although having said that I was just doing very well in a Poland game, preparing with my land forces for the not-very-sneak attack Ashurbanipal was building up to ... only for Catherine to declare war and send a large navy from out of nowhere that took Warsaw).
I have pretty much never had a problem with Alexander, despite his common appearance in polls like this - he's often a big militant civ like Germany, but doesn't seem to have any other tricks and despite his UA and reputation I can't recall seeing him try for diplo victory.
Was this pre-BNW? I've seen Attila a few times now in BNW and to my astonishment (on Immortal) he's almost always doing very well. His secret? He never attacks anybody in the early game, just settles down and builds up - in pre-BNW days he was always a nonentity because he'd overcommit to wars his AI was incapable of winning.
I did lose to him once through warfare in the early game (as Rome, appropriately enough), but I think that too was just pre-BNW.